Getting very old does not necessarily come with the absolute decline in mental and physical functioning that is commonly expected, new research shows.

A large-scale study of two groups of nonagenarians — people in their 90s — in Denmark finds that those born in 1915 not only lived longer than people born a decade earlier, but they also scored significantly better on measures of cognitive ability and activities of daily living.

Even after adjusting for increases in education in a decade, people born in 1915 "still performed better in the cognitive measures, which suggests that changes in other factors such as nutrition, burden of infectious disease, work environment, intellectual stimulation and general living conditions also play an important part in the improvement of cognitive functioning," says the study, published online today by the science journal The Lancet.

The findings challenge speculation that improving longevity "is the result of the survival of very frail and disabled elderly people," says lead researcher Kaare Christensen,professor of epidemiology at the University of Southern Denmark in Odense and director of the Danish Aging Research Center.

"That's not to say that everyone in the later cohort was healthy, smart and functioning well, but compared to those who were born 10 years earlier, not only were more living to a higher age, but they were functioning better," Christensen says.

Using the Danish Civil Register System, Christensen and colleagues identified all nonagenarians living in Denmark at the time that they were conducting their surveys. A total of 2,262 men and women born in 1905 were assessed in 1998 when they were ages 92 to 93. A smaller number, 1,584 men and women born in 1915, were assessed in 2010 when they were ages 94 to 95.

No one was excluded from the studies based on health, residence or cognitive status. When mental or physical handicap prevented a participant from responding (about 20%), someone else answered on his or her behalf. Along with an interview, the assessment consisted of physical tests (including grip strength, chair stand and gait speed) and cognitive measurements of attention, verbal memory and word fluency.

Results showed that the chance of surviving to age 93 years was 28% higher among those born in 1915; their chance of reaching 95 was 32% higher.

The two groups performed equally on tests measuring physical performance, but those born in 1915 outperformed those born in 1905 in activities of daily living such as walking inside and outside, getting out of bed and maneuvering up and down stairs. They also achieved better average test scores than those born in 1905, and a substantially higher proportion achieved maximum scores on cognition tests, even though they were older at the time of testing — leading to the suggestion that more people are living to older ages with better overall functioning.

"If this development were to continue, the future functional problems and care needs of very elderly people might be less than are anticipated on the basis of the present-day burden of disability," the study says.

The findings provide "impressive evidence that older today can be better than years past, especially in regards to brain health," says Sandra Bond Chapman, founder and chief director of the Center for BrainHealth at The University of Texas-Dallas. She was not involved in the study.

In 2010, Chapman and her team published research showing that engaging in cognitively challenging activities strengthens and preserves cognitive capacity as people age.

"Until recently, cognitive losses in aging were viewed as an inevitable consequence of living longer rather than a brain condition to be addressed," Chapman says. The data "provide hard evidence to inspire hope and motivation for the global graying and aging of the brain in developed countries."

An accompanying editorial in The Lancet adds that the study offers "good news" that "age-related cognitive decline in very elderly people is malleable" and "might even suggest the possibility of lowering the incidence or delaying the onset of dementia." Concerns about the rise in the prevalence of dementia in the oldest populations "plays an important part in the alarming predictions about the future global burden" of the disease, the editorial says.